The invention relates to geared power transmission systems, and more particularly, to geared drive ring couplers comprising drive rings that cooperate with a driver and driven pulley on a CVT transmission and wherein the drive rings mesh together and are connected by a bearing frame.
It is well known in the art that a gear type transmission may be used for operating a motor vehicle, motorcycle or the like. The transmission connects the motor to the drive wheels. Transmissions generally comprise a finite number of gears, usually three or four. Only one of the gears is most efficient, so operating the motor in one of the other gears necessarily reduces efficiency. For the purposes of improving fuel efficiency, a continuously variable transmission, or CVT, is preferable.
A CVT is infinitely variable so a wide range of gear ratios is made available as compared to a gear type transmission. The CVT transmission generally comprises a driver and driven pulley. The pulleys are connected by a belt trained around each. Various types of belts have been developed for use in continuously variable transmissions.
Generally, the CVT Belts have a silhouette similar to that of a conventional V-belt. In particular, they are broad at the top and narrow at the bottom and designed to fit between the sheaves of the pulley that defines an angular groove. The pulley on which the belt is trained comprises a moveable sheave and a fixed sheave, both having a truncated cone shape. Generally, one of the sheaves moves while the other remains fixed.
Moving one sheave in relation to the other effectively varies the effective diameter, xcfx86, of the pulley within which the belt operates. Consequently, belt linear speed is a function of the effective diameter of the pulley which is in turn a function of the axial position of the sheaves relative to each other.
Although the prior art CVT belts are flexible, each also has characteristics not found in other power transmission belts. For example, the belts are required to have transverse rigidity. This allows the belt to run at a particular effective diameter without being crushed between the pulley sheaves.
A drive ring may be used in a variable diameter pulley to change an effective diameter. A belt is then trained over the drive ring.
Regarding the prior art relationship between the pulley and the belt, U.S. Pat. No. 5,709,624 to Donowski discloses a variable diameter pulley. A single drive ring runs in the sheaves of the pulley. A flexible belt runs on the drive ring through the pulley. As the sheaves move with respect to each other, the effective diameter of the pulley is changed. Since the drive ring bears the transverse or compressive forces between the sheaves, the belt need not be designed to accommodate these forces. However, the Donowski device comprises a single drive ring used as a part of an auxiliary drive system of an internal combustion engine. A stabilizing member is also required to maintain the axis of rotation of the drive ring as least substantially parallel to the axis of rotation of the sheave members. The Donowski device does not lend itself to use in a CVT transmission.
Also representative of the prior art is U.S. Pat. No. 4,875,894 to Clark, which discloses a continuously variable transmission. The transmission comprises an input and output shaft, each having a rotary disk assembly. The rotary disk assemblies each have contact pads that form circles having continuously variable diameters. The two rotary disk assemblies are connected by a coupling mechanism, such as a single rigid coupling ring. Power transmission occurs between each pulley through rotation of the ring. This device does not offer the option of using flexible belts for power transmission, requiring instead the rigid ring to connect the two disks. This limits the space that the device can operate within, generally to a square or circular space defined by the extreme outer dimension of the pulleys.
What is needed is a geared drive ring coupler having co-operating drive rings that transmit power by gear interaction. What is needed is a geared drive ring coupler that has a frame for mechanically connecting and spatially orienting the drive rings. The present invention meets these needs.
The primary aspect of the invention is to provide a geared drive ring coupler having cooperating drive rings that transmit power by gear interaction.
Another aspect of the invention is to provide a geared drive ring coupler that has a frame for mechanically connecting and spatially orienting the drive rings.
Other aspects of the invention will be pointed out or made obvious by the following description of the invention and the accompanying drawings.
The invention comprises a geared drive ring coupler. The geared drive ring coupler comprises two pairs of adjacent drive rings rotatably connected to each end of a frame. Each pair of drive rings is meshed together with the cooperating pair of drive rings on the opposing end of the frame. The relative spatial arrangement of the axis of rotation of each set of drive rings is maintained by the frame, which in turn holds the drive rings in a predetermined relationship between the pulley sheaves. The drive rings on the driver pulley turn in the same direction as the driver pulley through frictional contact with the sides of the CVT driver pulley sheaves. The drive rings on the driven pulley side rotate in the opposite direction to the drive rings on the driver pulley, since they are meshed together. The driven drive rings are then in frictional contact with the sides of the driven pulley sheaves, thereby driving the driven pulley. The effective diameter or radius of each pulley is adjusted by movement of the pulley sheaves. Movement of the pulley sheaves causes the axis of rotation of each set of drive rings to move eccentrically with respect to the axis of rotation of their respective pulley. Since the drive rings are mechanically connected, the drive rings move with the frame as a unit in response to the movement of the pulley sheaves, thereby changing the effective gear ratio of the transmission.